The rath at Castletown in County Galway is a different proposition altogether. What survives here is barely a whisper in the landscape, a low broad swell of earth at the northern arc measuring just twenty centimetres above the interior and thirty-five above the exterior ground level. At twenty-eight and a half metres in diameter, the circular form is there if you know to look for it, but centuries of farming on undulating ground have reduced it to something you might walk across without pausing.

A rath is an enclosed farmstead of the early medieval period, typically defined by one or more earthen banks and ditches, and this one retains just enough to hint at its original structure. In the east-south-east sector, traces of external facing stones are still visible, suggesting the bank was once revetted in a more substantial way. Alongside these stones, faint traces of what may have been a fosse, the external ditch that would have accompanied the bank, can be made out. More intriguing still is the south-west quadrant of the interior, where there are traces of a possible souterrain. A souterrain is an underground stone-lined passage or chamber, commonly associated with ringforts and thought to have served for storage or as a place of refuge. Whether this one was ever fully constructed or remains simply a buried suggestion is unclear from what can be seen at the surface.